Incidence could drop below 0.1%

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Increasing the proportion of HIV-positive gay men in the UK
who have an undetectable viral load from the current figure of around 60% to 90% could result in a substantial drop in new HIV infections, a
modelling study suggests. In order to achieve this, it wouldn’t be enough to
change treatment guidelines – a substantial increase in HIV testing rates would
also be required, Andrew Phillips of University College London told the 21st Conference on Retroviruses and
Opportunistic Infections (CROI) in Boston last week.

However, Phillips noted that any decreases in current rates
of retention in care, treatment adherence or condom use could have a negative
impact on these predictions.

Reviewing the HIV epidemic among gay and other men who have
sex with men (MSM) in the UK, Phillips said that there are approximately
600,000 MSM in the country, of whom around 45,000 are living with HIV. While
approximately 20% are unaware of their infection, over 80% of diagnosed men are taking
HIV treatment and 95% of those on treatment have an undetectable viral load. In
all, approximately 60% of gay men living with HIV are virally suppressed.

His analyses suggest that while current provision of treatment
has curbed infections, its impact has been undermined by an increase in the
number of men having sex without a condom. Similar conclusions have been
reached by researchers looking at the gay epidemics in the Netherlands and
Switzerland. Moreover, epidemics of HIV in men who have sex with men continue
to expand in most countries of the world.

Future scenarios

Andrew Phillips then shifted his attention to predictions of
the potential impact of changes to treatment guidelines, or the uptake of HIV
testing, or both. His estimations are based on mathematical models which take into account multiple sources of data on the UK epidemic and varying assumptions
about sexual and testing behaviour.

In terms of policy changes, he considered the impact of immediately
recommending HIV treatment after diagnosis with HIV, rather than the current
treatment guideline of starting treatment with a CD4 cell count of 350 cells/mm3. The application of this policy should depend on the outcome of the START randomised trial, examining the impact of early treatment on the health of the person living with HIV.

He also considered the possibility of changes to HIV
testing, involving both an increase in the frequency of testing and a reduction
in the number of men who have never tested. At present, approximately 40% of men
are diagnosed within a year of acquiring their infection, but Phillips modelled
the impact of two possible scenarios:

A scale-up of testing, so that 60% are diagnosed within a
year of infection.

A larger scale-up, so that 90% are diagnosed within a year.

He did not know how such changes in testing behaviour could
be achieved, but did say that they were "highly ambitious" and would likely
require substantial investment.

The model forecast new infections up to the year 2030. It
predicted that if there was no change in treatment policy or in testing, over
3000 men who have sex with men would acquire HIV during the year 2030. However,
there is potential to reduce the number of infections through policy changes:

Immediate treatment could reduce infections by 32%.

A scale-up of testing could also reduce infections by 32%.

A larger scale-up of testing could reduce infections by 54%.

Immediate treatment and
a scale-up of testing could reduce infections by 64%.

Immediate treatment and
a large scale-up of testing could reduce infections by 80%.

In the latter scenario, around 600 gay and other men who
have sex with men would acquire HIV in 2030.

Preliminary analysis suggests that this
scenario would be highly cost-effective. Although many more people would be
taking HIV treatment in the first few years, the numbers on treatment would be
falling by 2030 as fewer men acquire HIV.

Phillips noted a number of factors which could influence
these outcomes. If retention in care and adherence deteriorated, so that 15% fewer
men with HIV had an undetectable viral load, there would be around 1000 more
infections each year.

Changes in sexual behaviour could also have an impact – a
decrease in condom use is possible as the impact of treatment on transmission
becomes better known. However, the effect of this would vary in the different
scenarios.

If testing and treatment policy does not change, a
relatively small increase of 10% more men having sex without a condom each year
would result in a massive increase in infections – up to around 6000 in the
year 2030.

In the scenario of immediate
treatment and a large scale-up of testing, there would be a smaller pool
of men with infectious HIV, so the impact of sexual behaviour change would be lesser. A 10% increase in sex without a condom would result
in a few hundred more infections each year.

Phillips also suggested that in the most optimistic
scenario, primary infection might have less impact on the epidemic
than it does at present. He said that the effective treatment of men who have
chronic infection would help prevent outbreaks of primary infection
occurring.

Summing up

Phillips’ analyses suggest that if the current situation is
maintained – in which around 60% of men living with HIV have an undetectable
viral load – over 3000 men will acquire HIV each year.

If fewer men are virally suppressed, infection rates would
be dramatically higher. If 30% of men had an undetectable viral load, well over
10,000 men would be newly infected each year.

But an improvement of viral suppression rates to 90% could
result in only around 600 annual infections, an incidence of less than 1 per
1000 person-years.

He concluded by noting that to achieve the 90% viral
suppression rate, it will be necessary for 90% of men to be diagnosed within a year
of infection; for treatment to begin immediately after diagnosis; for linkage,
retention and adherence to remain good; and for levels of condomless sex not to
increase.

Reference

Phillips A MSM in the UK: Prevention Effects of ART in Perspective. 21st Conference on Retroviruses and Opportunistic Infections, Boston, abstract 116, 2014.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.